I'm trying to run example from Hibernate reference: Customer/Order/Product.

Mapping is this:

<class name="Order" table="orders">
<id name="id">
<generator class="native"/>
</id>
<property name="date"/>
<many-to-one name="customer" column="customer_id"/>
<list name="lineItems" table="line_items">
<key column="order_id"/>
<list-index column="line_number"/>
<composite-element class="LineItem">
<property name="quantity"/>
<many-to-one name="product" column="product_id"/>
</composite-element>
</list>
</class>

In table Order I have one order and in table line_items I have one lineItem for this Order.

But, when I try to load Order:

...
order = (Order)session.load(Order.class, orderId);

In this order object's list of lineitems, first lineitem is always null, and second is good lineitem.

What is the problem ?

Most likely, you don't have any rows with line_number = 0. If line_number starts from 1 and goes up, add the attribute 'base="1"' to the list-index element.

O.K. it is working, but why I don't have element in list with index 0 ? I have one order and one lineitem for this order only.

When you created the Order object the first time, in order to save it, where did you put the LineItem? If you did this, you'll have put it in position 1:The list that you get back when you re-load the order will have a 0 index (all java lists do), so it'll be null.

I have something wierd here, when I load Order with session.load (Order.class, orderID) it loads Order and LineItems, but when I insert new LineItem in Order and try to saveOrUpdate, there is nothing inserted in database. But, also there is no error.

When you created the Order object the first time, in order to save it, where did you put the LineItem?

I'm adding LineItems like this:

order.getLineItems().add(item).

It seems that i forgot to set cascade on Order. Now, when I set it, and call saveOrUpdate on Order, it generates this error:

org.hibernate.StaleStateException: Batch update returned unexpected row count from update: 0 actual row count: 0 expected: 1

?

O.K. I found error:

It's been

<id name="id" column="id" type="long" unsaved-value="null">

but, because it is long (not Long) I assume that this must be:

<id name="id" column="id" type="long" unsaved-value="0">

I have problem to insert a new Customer and his Orders:

this is schema:

<class name="Customer" table="customers">
<id name="id">
<generator class="native"/>
</id>
<property name="name"/>
<set name="orders" inverse="true">
<key column="customer_id"/>
<one-to-many class="Order"/>
</set>
</class>

problem is that Customer is not commited, and when orders are trying to insert they don't know for Customers id. How to Customer be first inserted and then to orders be inserted ?

I forget, concrete error is:

Field 'customer_id' doesn't have a default value

org.hibernate.exception.GenericJDBCException: could not insert: [org.package.Order]

Add 'not-null="true"' to the <key> element.
You probably also want to remove 'inverse="true"', as that tells hibernate not to insert or delete Orders just because they've been added to Customer's set.